TCP Transport RuntimeError with Python 3.13 + uvloop

[dylangroos]

TCP Transport RuntimeError with Python 3.13 + uvloop

Summary

uvloop is causing RuntimeError: unable to perform operation on <TCPTransport closed=True> errors when used with Python 3.13. Switching to --loop asyncio fixes the issue.

Environment

• Python: 3.13.3
• uvloop: (latest)
• Starlette: 0.46.2
• FastAPI: 0.115.14

Reproduction

1. Use Python 3.13
2. Run uvicorn with --loop uvloop
3. Make concurrent HTTP requests (e.g., browser loading static files)
4. Client disconnects/refreshes during response

Workaround

Use --loop asyncio instead of uvloop.

Expected

uvloop should handle closed connections gracefully like asyncio does.

Edit

I had a stray uvicorn process that had wracked up 9hrs of CPU time, this could potentially be the issue?

[Kludex]

Is this the same as #506 (comment) ?

[dylangroos]

Let me take a look... will provide more info if need be. Thank you